1. Field of the Invention
This invention relates to a process for plasma etching, and more particularly to a process for etching silicon or various silicon compounds by plasma etching.
2. Description of the Prior Art
In the production of various semi-conductor devices, the so-called "dry process" has been much used to make patterning or perforation of semi-conductor substrates, insulating films or semi-conductor films without using chemicals or water. That is, the so-called, conventional "wet process" using a large amount of various acids, alkalis, organic solvents or the like has many problems such as a large possibility of contamination by impurities contained in the chemicals; swelling of the resist film used as a mask, making the shape irregular, inevitable occurrences of undercut, etc.
In the field of integrated circuit production, a large effort has been recently made to improve the degree of integration, but it is necessary to make far finer wiring, perforation, or other processings more precisely than before to improve the degree of integration. The wet process, where the swelling of resist and undercut are inevitable, is naturally not suitable for such finer processings. The dry process using no such chemicals thus is preferable, and a dry process based on plasma etching is now most widely employed among the available dry processes.
Plasma etching is defined as a process of introducing a halogen compound such as CF.sub.4, CCl.sub.4, BCl.sub.3, etc. or further admixed with O.sub.2, N.sub.2 , Ar or air into a reactor tube under a specific pressure, generating a plasma within the reactor tube, and etching a material to be etched in the reactor tube by radicals formed by the plasma.
Various apparatuses are used for plasma etching, but a "planar type" apparatus comprises of two flat electrode plates placed parallel to each other in a reactor tube, and a "barrel type" apparatus comprised of semiannular electrodes placed around the outside of a reactor tube against each other are most widely used, and a high frequency power such as 13.56 MH.sub.z is applied thereto as a power for generating plasma.
When the etching is carried out by means of these plasma etching apparatuses, the drawbacks of said conventional wet process can be much improved, and it is expected to use the process for plasma etching in the production of semi-conductor integrated circuits with a high degree of integration much more in the future. However, etching of silicon or silicon compounds, which undergo etching to the largest degree, still has problems to be solved in etching rate, selectivity, detection of etching end point, etc., and these problems have been difficult to solve.